There has been known a conventional technology which uses a marking device to mark two-dimensional codes, characters, logo marks, images, and the like on a transparent polycarbonate material.
The polycarbonate is a transparent material in a pure state, and is generally excellent in shock resistance, weather resistance, electrical insulation, dimensional stability, and the like.
A conventional method to mark characters and the like on the polycarbonate often employs inkjet printing.
However, the conventional printing by means of the inkjet directly attach ink to a surface of the transparent polycarbonate, and there pose such problems that the applied ink is separated by a contact, is subject to a secular change, and is inferior in durability.
In order to solve these problems, there has been developed a technology which performs marking by means of a laser beam on the polycarbonate material (refer to Japanese Laid-Open Patent Publication (Kokai) No. H5-337659, line 7 of second column to line 10 of third column, for example: Document 1).
The patent document 1 describes laser marking on the polycarbonate material in the following way.
Namely, there is described a method and a marking device, which perform marking by irradiating a repetitively pulsed YAG laser beam on a workpiece made of a polycarbonate material, thereby transforming the color of a component material at the irradiated position to black.
However, according to the conventional laser marking method for the polycarbonate, even if the marked portion has changed the color thereof to brown to black, marked images, characters, and the like have high light transmittance, and thus have a defect of inferior visibility, and there poses such a problem that the sole polycarbonate can hardly be applied to products such as cards.
Moreover, since the visibility of the marked images and characters is low, it is difficult to mark an image such as a photograph which requires a fine adjustment of density changes on the polycarbonate.
It is an object of the present invention to solve the above problems by providing a laser marking device and a laser marking method which, upon marking an image or the like read by a scanner or the like on the polycarbonate, mark the image which bares comparison with the original image by adjusting the dot depth and the dot diameter.
Moreover, it is another object of the present invention to provide a laser marking device and a laser marking method which build up a polycarbonate material and a resin material, and perform marking such that two-dimensional codes, characters, logo marks, images, and the like appear clearly and hovering three-dimensionally.